Adaptation of turbo coding and equalization in turbo equalization for time-varying and frequency-selective channels

A number of authors have sought to combine equalization and decoding in an iterative system in order to reduce the effects of frequency and temporal dispersiveness of time-varying frequency-selective channels. In the recent literature, several architectures based on these iterative systems have been...

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Bibliographic Details
Published in:Canadian journal of electrical and computer engineering 2008-01, Vol.33 (2), p.99-108
Main Authors: Berdai, A., Chouinard, J.-Y., Huu Tue Huynh
Format: Article
Language:English
Subjects:
Cancellers
Channel estimation
Channels
correlation du bruit
Decision feedback equalizers
Decoders
Dispersion
Equalization
Equalizers
facteur de fiabilite
Filters
Frequency estimation
Interference
Interference cancellation
Iterative decoding
Iterative methods
Noise reduction
reliability factor
Temporal logic
Time varying systems
turbo
turbo codage
Turbo codes
turbo coding
turbo egalisation / noise correlation
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Summary:A number of authors have sought to combine equalization and decoding in an iterative system in order to reduce the effects of frequency and temporal dispersiveness of time-varying frequency-selective channels. In the recent literature, several architectures based on these iterative systems have been proposed. One can note architectures which combine a maximum a posteriori (MAP) equalizer and decoder, architectures formed by an interference canceller and MAP decoder, architectures implementing a decision feedback equalizer and a MAP decoder, etc. Most of these architectures require accurate channel estimation to adapt the equalizer filters or to execute the MAP equalizers. This article presents a turbo equalizer architecture for time-varying frequency-selective channels without channel estimators. The proposed turbo equalizer consists of an interference canceller in direct-adaptation mode and a turbo decoder. In order to reduce noise correlation, the addition of a transverse filter to the interference-canceller architecture is proposed. The reliability factor for variable time-varying frequency-selective channels is also redefined in order to improve the performance of the turbo decoder. The architecture of the proposed turbo equalizer reduces considerably the effects of frequency and temporal dispersiveness of time-varying frequency-selective channels depending on the normalized Doppler frequency range.
ISSN:0840-8688
2694-1783
DOI:10.1109/CJECE.2008.4621834